1. Field of the Invention
The present invention relates to a plate-shaped catalyst and a method of producing the same, and more particularly to a plate-shaped catalyst for denitration using an expanded metal strip as a base plate.
2. Description of the Related Art
U.S. Pat. No. 4,567,630 discloses a plate-shaped catalyst for denitration using an expanded metal strip as a base plate. A method for producing this plate-shaped catalyst mainly includes: a step of forming an expanded metal strip; a step of spray-coating molten metal onto the expanded metal strip to form roughened surfaces thereon; a step of coating a catalytic substance onto the thus surface-roughened expanded metal strip; a step of holding the catalyst coated between upper and lower sheets to protect the surfaces thereof; a step of applying pressure to the catalyst strip to closely attach the catalytic substance onto the roughened surfaces for flattening the surfaces out; a step of press-working the thus obtained catalyst strip to form it into a predetermined shape; and a step of cutting the catalyst strip to the specified length to obtain a plate-shaped catalyst. During the above-described steps, the plate-shaped catalyst strip which is prepared by coating the catalytic substance onto the expanded metal strip is pressed to form V-shaped ridges on both surfaces thereof. The shaped catalysts are obtained by cutting the catalyst strips and piling them up on each other by using the ridges as spacers, and to form a catalytic unit. When the catalyst unit is used as an exhaust gas denitrating catalytic unit, exhaust gases mixed with a reducing agent such as ammonia are passed through a multiplicity of channels formed by the ridges of the piled-up upper and lower plate-shaped catalysts, whereby nitrogen oxides (NOx) contained in the exhaust gases catalytically are reacted with ammonia in the exhaust gases, so that the exhaust gases can be purified.
In the aforesaid plate-shaped catalyst unit, the expanded metal strip is pressed to form the ridges. The ridges have a V-shape cross section, which function as the spacer. After coating the catalyst substance onto the expanded metal strip, the expanded metal strip is bent into the form that is V-shaped in cross-section, whereby the expanded metal strip is reduced in size in a direction of bending. For this reason, in order to obtain the plate-shaped catalyst unit having the predetermined length, it is necessary to use the expanded metal strip having a size that allows for the reduction in size due to the aforesaid pressing. For example, in order to finish the expanded metal strip to the width of 500 mm, it is necessary to use an expanded metal strip having a width of about 525 mm.